The present invention relates to a fluid flow control apparatus for use in, for example, supplying a process gas for manufacturing semiconductors.
In a process for manufacturing semiconductors, there has been an increasing demand for a flow rate control apparatus for gasifying a liquid or solid material at a high temperature and feeding the resultant gas in a stable manner.
The above-mentioned flow rate control apparatus is used in a high-temperature environment of 100.degree. C. or more. Therefore, as a control valve for the above-mentioned flow rate control apparatus, an electromagnetic valve adapted for use at a high temperature has been conventionally used. However, even in the electromagnetic valve adapted for use at a high-temperature, the heat-resistance of a coil is limited, so that a usable maximum temperature for the electromagnetic valve is about 200.degree. C. Further, many materials used for manufacturing semiconductors are chemically reactive. Therefore, a diaphragm-operated control valve has been strongly desired.
However, in a diaphragm-operated control valve, the actuator for the valve is required to generate a force as large as 10 kg/cm.sup.2 or more. Such a large force cannot be obtained when the actuator is an electromagnetic valve. Therefore, it is difficult to enable the use of a diaphragm-operated control valve by using an electromagnetic valve.